Phytate is the major storage form of phosphorus in cereals and legumes. However, monogastric animals such as pigs, poultry and fish are not able to metabolise or absorb phytate (or phytic acid) and therefore it is excreted, leading to phosphorous pollution in areas of intense livestock production. Moreover, phytic acid also acts as an antinutritional agent in monogastric animals by chelating metal agents such as calcium, copper and zinc.
In order to provide sufficient phosphates for growth and health of these animals, inorganic phosphate is added to their diets. Such addition can be costly and further increases pollution problems.
Through the action of phytase, phytate is generally hydrolysed to give lower inositol-phosphates and inorganic phosphate. Phytases are useful as additives to animal feeds where they improve the availability of organic phosphorus to the animal and decrease phosphate pollution of the environment (Wodzinski R J, Ullah A H. Adv Appl Microbiol. 42, 263-302 (1996)).
The addition of phytase to broiler feed has also been shown to increase the apparent metabolisable energy (AME), the availability of nitrogen and amino acids (Ravindran, V. et al, Brit. Poultry Sci. 41, 193-200 (2000)).
A number of phytases of fungal (Wyss M. et al. Appl. Environ. Microbiol. 65 (2), 367-373 (1999); Berka R. M. et al. Appl. Environ. Microbiol. 64 (11), 4423-4427 (1998); Lassen S. et al. Appl. Environ. Microbiol. 67 (10), 4701-4707 (2001)) and bacterial (Greiner R. et al Arch. Biochem. Biophys. 303 (1), 107-113 (1993); Kerovuo et al. Appl. Environ. Microbiol. 64 (6), 2079-2085 (1998); Kim H. W. et al. Biotechnol. Lett. 25, 1231-1234 (2003); Greiner R. et al. Arch. Biochem. Biophys. 341 (2), 201-206 (1997); Yoon S. J. et al. Enzyme and microbial technol. 18, 449-454 (1996); Zinin N. V. et al. FEMS Microbiol. Lett. 236, 283-290 (2004)) origin have been described in the literature.
However, fungal phytases tend to be proteolytically unstable (Igbasan F. A. et al. Arch. Anim. Nutr. 53, 353-373 (2000)) and therefore susceptible to degradation, while some bacterial phytases have a narrow substrate specificity for phytate alone and poorly degrade inositol phosphates of intermediate degrees of phosphorylation (Greiner R. et al., Arch. Biochem. Biophys. 303 (1), 107-113 (1993); Kerovuo J et al, Biochem. J. 352, 623-628 (2000)).
Furthermore, it is known that the interaction of calcium with phytate to form Ca-phytate complexes is detrimental to phytase activity (Selle, P. H. et al, Livestock Science. 124, 126-141 (2009)). The calcium in these Ca-phytate complexes has been hypothesised to make phytate inaccessible to the phytase or to compete with non-complexed phytate for the active site of the enzyme (Long, C., Phytase, Biochemists Handbook, Princeton, N.Y., Van Nostrand-Reinhold (1961); Wise, A., Nutrition Abstracts & Reviews, 53, 791-806 (1983)).
The addition of phytase has been shown to increase the AME of a high phytate diet. Ravindran et al (Br. Poult. Sci., 2000, 41, 193-200) has suggested that calcium phytate complexes react with fatty acids to form insoluble soaps in the gut lumen, thereby lowering fat digestibility. The addition of phytase has been suggested to reduce the level of these soaps. Supporting this hypothesis, there is evidence of phytate interactions with lipid in corn (Cosgrove, 1966, Rev. Pure App. Chem. 16:209-224). These ‘lipophytins’ have been described as a complex of Ca/Mg-phytate, lipids and peptides (Cosgrove, 1966, Rev. Pure App. Chem. 16:209-224). Other reports have also suggested interactions between Ca, fat and phytate in the diet. For instance, Matyka et al. (1990) (Anim. Feed. Sci. Technol. 31:223-230) found that dietary tallow reduced phytate P utilization in young chicks, and increased the percentage of fat excreted as soap fatty acids.
The addition of exogenous lipases has had limited success in increasing lipid and mineral digestibility. However, this may have been limited by the formation of complexes of free fatty acids bound with Ca and phytate (Cosgrove, 1966 supra), which are insoluble in the gastro intestinal tract, and poorly absorbed (Matyka et al. 1990 supra).
The use of exogenous lipases in animal feed has been previously suggested with the objective to improve the fat digestion by animals. Lipase is hypothesised to improve digestion as it liberates absorbable free fatty acids (FFA) faster than otherwise would have happened. However, attempts to demonstrate improvements in animal performance or digestibility by the use of exogenous lipases have been at best inconsistent and have often showed lipases not to work. Dierick and Decuypere (2004) (J. Sci. Food Agric. 84:1443-1450) showed no improvements in fat digestibility with addition of a microbial lipase in pig diets. Hurtado et al. (2000) (Rev. Bras. Zootec. 29:794-802) failed to detect increments of body weight gain, feed efficiency and energy digestibility due to the use of an exogenous lipase in piglets. Additionally, they reported no additive effects in any of these parameters when such lipase was combined with an amylase and a protease. Officer (1995) (Anim. Feed Sci. Technol. 56:55-65) reported no significant changes in body weight gain of feed intake of piglets by the use of two combinations of exogenous enzymes which they described as lipase, proteinase, B-glucanase, amylase and cellulose, and lipase, B-glucanase, hemi-cellulase, pentosanase, cellulose, amylase and proteinase.
In broiler chickens, Meng et al. (2004) (Poult. Sci. 83:1718-1727), when using a bacterial lipase in wheat-based diets, failed to detect any effect of the lipase on apparent digestibility of fat, starch, nitrogen and NSP, as well as AME. Additionally, they rejected the hypothesis that a combination of carbohydrases, including xylanase, glucanase and cellulase, on top of the lipase would increase the lipase effects on nutrient digestibility by reducing viscosity of the digesta and increasing fat digestion and absorption.
Al-Marzooqi and Leeson (1999) tested lipases from animal origin and pancreatic extracts. Although they were able to demonstrate improvements in fat digestibility and reductions on the level of soaps at the faecal levels when these additives were used in the diet, they also reported an anorexic effect (reduction of feed intake), which they explained by possible contaminations with cholecystokinin in this type of extracts. This fact limits its utilization in animal feed and possible improvements in growth or feed efficiency in animals.
One aim of the present invention is to provide a feed supplement which provides improved availability of at least one nutrient or an improvement in the apparent metabolisable energy from a feed material.